However, other approaches can be used to measure halo concentration. In particular, [1]} stacked \(\sim 1000\)  systems from the CS82 survey [2]} in different magnitude-gap bins, the larger of which has mean \(\Delta m_{12} \sim 1.7\) . They cross-correlate weak lensing measurements with NFW parametric mass profiles to measure masses and concentrations of their sample. They found that halos in the \(\Delta m_{12} \sim 1.7\)  bin have a higher probability to be more concentrated and, thus, probably formed earlier.
